This issue is two folds: 1) Is the coop responsible if the sediments in the pipes reaches the faucets of the shareholders? Sediment in pipes is a normal occurrence so I would say that is not the Coop responsibility even if the sediment moved around because of a repair. 2) Is the coop responsible for the plumber's bill? From your description it sounds like you asked for a plumber and a plumber was sent to your unit. The Super could have handled this better but if you ask for a plumber and the job is not a coop issue, the bill is on you. About the bill amount: Unfortunately Coops can only hire vendors who carry adequate (very high coverage) insurance policies and the cost is passed back to the client. $400 for a house call is average in NYC these days. Next time ask the super to do the work and hand him a $20 (Yes, he should be paid because when he does something that is the shareholder's responsibility, the super is working for you, not the Coop.).